Explanation

A is correct because Hazrat Musab ibn Umair (RA) was the first preacher sent by Prophet Muhammad (SAW) to Madina. B is incorrect because there is no historical record confirming Jafar Tayyar (RA) as the first preacher in this context. C is incorrect because Ayub Ansari (RA) was not appointed for this specific role. D is incorrect because Hazrat Usman (RA) was a companion, but not the first designated preacher to Madina.